JPS6217110B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a unit injector used in a diesel engine.

Generally speaking, unit injectors, unlike in-line fuel injection pumps or distribution-type fuel injection pumps, are installed directly on the cylinder head of a diesel engine without using a high-pressure injection pipe, and are installed directly on the diesel engine's cam. They have been configured to be driven by a shaft to inject fuel.

Typically, this type of unit injector has a plunger with a reed rotated by a control rack to vary the effective stroke of the plunger to meter the amount of fuel injected.

However, since such a unit injector is equipped with its own control rack, when installed in the cylinder head of a diesel engine, the structure around the cylinder head becomes extremely complex, and the unit injector Camshaft as a drive system connection
Considering the mounting position of the push rod, rocker arm, etc., the mounting position of the unit injector is limited to an extremely narrow range, making it difficult to effectively utilize the space in the cylinder head.

In addition, in recent years, a configuration has been developed in which fuel that has been regulated to a predetermined pressure is metered using a throttle and sent to a pump chamber, and then the high-pressure fuel drives a plunger to inject the fuel in the pump chamber. Unit injectors have been proposed that are equipped with a free piston type metering plunger in a plunger bore and configured to meter the fuel injected by the metering plunger. However, in the unit injector, where fuel is metered by the throttle, when the fuel passes through the throttle and is sent to the pump chamber, air bubbles are generated, making the injection amount unstable or causing problems at the injection timing. In addition, a unit injector metered by a free piston type metering plunger has a complicated structure, and it is difficult to obtain the desired injection amount and timing. The component parts of the unit injector required extremely high machining accuracy.

An object of the present invention is to prevent the generation of air bubbles in a pump chamber, to properly measure the amount of fuel in the pump chamber, to obtain a desired fuel injection amount and injection timing, and to improve the engine performance of a diesel engine. An object of the present invention is to provide a unit injector used in a diesel engine which simplifies the structure around the cylinder head when it is attached to the cylinder head of the diesel engine.

In view of these problems, the unit injector used in the diesel engine of the present invention includes a needle spindle bore having a valve seat and a nozzle, a plunger bore connected to a fuel reservoir of the needle spindle bore, and , widening the plunger bore at a predetermined portion of the plunger bore;
a valve body having a slider bore in communication with the plunger bore; and a nozzle needle fitted in the needle spindle bore so as to be seated in the valve seat by a needle spring. , the plunger
a plunger reciprocatingly slidably disposed in the plunger bore so as to form a pump chamber within the bore, the plunger comprising a lead and a communication passage connecting the lead to the pump chamber; Fitted into the plunger so as to form a fuel chamber and a hydraulic chamber, and connected to the inner peripheral surface of the slider bore by a helical spline, the slider bore is reciprocably disposed within the slider bore, and a control slider having a feed hole that connects the fuel chamber to the lead of the plunger; a slider return spring disposed in at least one of the fuel chamber and the hydraulic chamber; The valve body includes a fuel passage formed in the valve body so as to communicate with the pump side, and an oil passage formed in the valve body so as to communicate the hydraulic chamber with the control oil pump side. It consists of

Hereinafter, preferred embodiments of the unit injector used in the diesel engine according to the present invention will be described with reference to the drawings.

1 to 4 show a specific example 10 of a unit injector used in a diesel engine according to the present invention.

The unit injector 10 is a valve
A needle spindle bore 19 having a seat 20 and a plurality of nozzles 21, 22, a plunger bore 31 communicating with the fuel reservoir 23 of the needle spindle bore 19, and an upper part of the plunger bore 31. , a valve body 11 having a slider bore 32 connected to the plunger bore 31 with the plunger bore 31 concentrically widened, and seated on the valve seat 20 by a needle spring 49. The nozzle fitted in the needle spindle bore 19 as shown in FIG.
A pump chamber 3 is located within the needle 24 and its plunger bore 31 on the fuel reservoir 23 side.
4, its plunger bore 31
A plunger 33 is arranged to be able to reciprocate and slide, and is provided with a lead 35 near the tip and a communication passage 36 that connects the lead 35 to the pump chamber 34, and a fuel chamber 4 in the slider bore 32.
0 and the plunger 33 so as to form a hydraulic chamber 41, and is helically spline-coupled to the inner circumferential surface of the slider bore 32, and is reciprocably disposed within the slider bore 32. In addition, a control slider 38 is provided with a feed hole 39 that can connect the fuel chamber 40 to the lead 35 of the plunger 33, and a slider disposed in the fuel chamber 40.
A fuel passage 44 formed in the valve body 11 and a hydraulic chamber 41 are connected to a control oil pump so that the return spring 42 and its fuel chamber 40 can be connected to a feed pump (not shown). (not shown) so that the side can be contacted.
The valve body 11 includes an oil passage 46 formed in the valve body 11.

The valve body 11 has a nozzle 13 and a needle spring guide 1 integrated by a nut 12 and a plunger guide 17 screwed together.
4, a partition plate 15, and a slider guide 16.

That is, the valve body 11 includes a nut 12 formed in a cylindrical shape with a nozzle fitting hole 18 at the lower end, and is fitted into the nut 12 so that the lower end side protrudes from the nozzle fitting hole 18. and a nozzle 13 having a valve seat 20 and a needle spindle bore 19 having a plurality of nozzles 21 and 22, and is fitted into the nut 12 so as to be placed on the upper end surface of the nozzle 13, and a needle spring chamber 26 which is open at the top and is disposed substantially coaxially with the needle spindle bore 19.
a needle spring guide 14 having a needle spring guide 14, a partition plate 15 fitted into the nut 12 so as to close the open end of the needle spring chamber 26, and the partition plate 1.
A plunger bore 31 that is fitted into the nut 12 and extends in the axial direction so as to rest on the upper end surface of the nut 12;
In the upper part of the plunger bore 3
A cylindrical slider guide 16 having a slider bore 32 connected to a plunger bore 31 of the nozzle 1 so as to spread out in a circular manner, and a nozzle 1 thereof.
3, a needle spring guide 14, a partition plate 15, and a plunger guide 17 screwed into the upper end of the nut 12 so as to secure the slider guide 16 within the nut 12.

Of course, the nozzle 13, the needle spring guide 14 and the partition plate 15 are connected to the fuel passages 25, 29 and 30, which are in communication with each other.
respectively, and the plunger bore 31 is connected to the fuel reservoir 2 of the needle spindle bore 19.
I am contacting 3.

Nozzle needle 24 is reciprocally slidably disposed in needle spindle bore 19 so as to be seated on valve seat 20 in nozzle 13 .

The nozzle needle 24 has a pin 28 at its upper end.
is integrally provided, and the pin 28 is connected to the needle.
Pin hole 2 formed at the lower end of the spring guide 14
7, the tip of the pin is in contact with the spring seat 50 disposed within the needle spring chamber 26, and the needle spring 49 disposed within the needle spring chamber 26 always closes the valve seat. It is pressed to 20.

The plunger 33 has its plunger bore 31
to form a pump chamber 34 at a position below the
It is arranged in the plunger bore 31 so as to be able to slide back and forth.

That is, the plunger 33 is housed in the plunger bore 31 so as to form the pump chamber 34 at the position on the partition plate 15 side, and the lower end and upper portion thereof are connected to the slider guide 16 of the valve body 11. and is supported by the plunger guide 17 so as to be able to slide back and forth.

Of course, the pump chamber 34 is connected to the above-mentioned fuel passage 2.
5, 29, 30 to the fuel reservoir 23 of its needle spindle bore 19.

Further, as described above, in a state where the plunger 33 is supported by the valve body 11 so as to be able to reciprocate and slide, the portions of the plunger 33 other than the lower end portion and the upper end portion are connected to the slider bore. Of course, it is spaced apart from the inner circumferential surface of 32 with a predetermined gap maintained therebetween.

Furthermore, a lead 35 is formed on the outer circumferential surface of the plunger 33 at a position corresponding to approximately the center of the slider bore 32, and a lead 35 is formed inside the plunger 33 at a position near the lower end of the pump chamber. A communication path 36 is formed which communicates with 34.

Of course, the plunger 33 has a follower part 37 at its upper end, and a valve spring 48 is arranged between the follower part 37 and the upper end surface of the plunger guide 17.

The control slider 38 is fitted into the plunger 33 so as to form a fuel chamber 40 at a lower position and a hydraulic chamber 41 at an upper position within the slider bore 32 in the slider guide 16 of the valve body 11. In addition, they are helically spline-coupled to the inner circumferential surface of the slider bore 32 and are reciprocatably disposed within the slider bore 32.

That is, a helical spline groove is formed on the outer peripheral surface of the control slider 38, and a helical spline that meshes with the outer peripheral surface of the control slider 38 is formed on the inner peripheral surface of the slider bore 32. It is formed.

Therefore, the control slider 38 is
Within the slider bore 32, it is allowed to reciprocate up and down with rotational motion.

The control slider 38 also controls the fuel chamber 40 from the plunger 33 when the plunger 33 slides back and forth into position.
Feed Hall 39 Contacting Lead 35 of 3
furthermore, at a position opposite to the feed hole 39, the lead 35 is connected to the fuel chamber 40.
It is equipped with a spill hole 43 that connects to the

A slider return spring 42 is located in the fuel chamber 40 and is attached to the control slider 3 when the diesel engine is stopped.
8 to the starting position.
The slider 38 is pushed upward.

The fuel passage 44 feeds the fuel chamber 40.
It is formed in the valve body 11 so as to be able to communicate with the pump (not shown) side.

That is, the fuel passage 44 has one end, in other words, the fuel port 45 connected to the valve body 11.
The plunger guide 17 and the slider guide 16 of the valve body 11 are formed so as to open on the side of the plunger guide 17 of the valve body 11 and communicate with the fuel chamber 40 at the other end.

The oil passage 46 is formed in the valve body 11 so as to communicate the hydraulic chamber 41 with a control oil pump (not shown).

That is, the oil passage 46 opens one end, in other words, the hydraulic port 47 to the side of the plunger guide 17 of the valve body 11,
The other end is formed in the plunger guide 17 so as to communicate with the hydraulic chamber 41.

The unit injector 10 configured as described above has its nozzles 21 and 22 housed in a combustion chamber in the cylinder head of a diesel engine (not shown), and the follower portion 37 of its plunger 33 in the cylinder head of a diesel engine (not shown). It is attached to the cylinder head of the engine in such a way that it contacts the cam surface of the camshaft.

In the unit injector 10 thus mounted on the cylinder head, the fuel port 45 of its fuel passage 44 is connected to the supply port of the feed pump via a fuel line (not shown).

Further, a hydraulic port 47 of the oil passage 46 in the unit injector 10 is connected to a supply port of a control oil pump (not shown) via a hydraulic pipe (not shown).

The control oil pump is configured in much the same way as the hydraulic governors used in existing diesel engines, i.e., the control oil pump depends on the amount of accelerator pedal depression of the vehicle in which the diesel engine is installed. Hydraulic pressure is generated according to the number of rotations of the diesel engine, and the hydraulic pressure is sent to the hydraulic port 47.

Next, to explain the operation of the above-mentioned unit injector 10, first, fuel from the feed pump is sent to the fuel port 45, and when the plunger 33 slides back and forth due to the rotation of the cam shaft, the plunger At a predetermined position in the sliding stroke range of 33, the control slider 3
8 feed hole 39 is the plunger 33
lead 35 of the unit, and fuel is metered into the pump chamber 34 from the control oil pump to the hydraulic port 47 of the unit injector 10. controlled by hydraulic oil.

That is, the pressure oil from the control oil pump is sent to the hydraulic chamber 41 of the unit injector 10, and the pressure in the hydraulic chamber 41 is
The pressure of the fuel in the fuel chamber 40 and the slider
When the force of the return spring 42 is exceeded, the control slider 38 slides downwardly, rotating in the direction of the arrow shown in FIG.

As the control slider 38 rotates and slides downward in this manner, the control slider 38 and the plunger 33
from the state shown in the figure to the state shown in FIG.
The relative position of the feed hole 39 and the lead 35 of the plunger 33 is changed, and the communication between the feed hole 39 and the lead 35 allows the metering of fuel within the pump chamber 33. It will be done.

Of course, the feed hole 39 and lead 35
The relative positional deviation with respect to the control slider 38, that is, the rotation angle and vertical movement distance of the control slider 38 are determined according to the pressure of the pressure oil sent to the hydraulic chamber 41.

Furthermore, if the inclination angle of the lead 35 is made the same as the helical spline groove angle of the control slider 38, the fuel injection timing becomes constant, and if the inclination angle and the torsion angle are made different, Of course, the timing of fuel injection changes.

The fuel metered in the pump chamber 34 in this way is compressed in the pump chamber 34 by pushing the plunger 33 through the cam shaft, and the compressed fuel is transferred to the fuel passage 3.
Needle spindle via 0, 29, 25
The fuel is sent to the fuel reservoir 23 in the bore 19.

Further, when the plunger 33 is pushed in and the fuel pressure in the fuel reservoir 23 reaches a predetermined pressure, the nozzle needle 24
is lifted against the needle spring 49, and a predetermined amount of fuel is injected in the form of a mist under high pressure from the injection ports 21 and 22.

According to the invention configured as above, the control slider is reciprocated with the rotational motion by the pressure oil from the control oil pump, and the feed hole of the control slider and the lead of the plunger are connected. Owing to the change in relative position, the metering of fuel in the pump chamber of the unit injector is ensured by the pressure oil from its control oil pump, and in particular when metering the fuel. In the communication between the feed hole and its lead, the fuel is not excessively throttled, the generation of bubbles in the pump chamber is prevented, injection pressure loss is reduced, injection delay is prevented, and the end of injection is prevented. This improves the engine performance of diesel engines by providing a predetermined fuel injection amount and injection timing, and does not include the control rack used for fuel metering in existing unit injectors. Therefore, when it is attached to the cylinder head of a diesel engine, the structure around the cylinder head is simplified and becomes extremely practical.

[Brief explanation of the drawing]

FIG. 1 is a vertical sectional view showing a specific example of a unit injector used in a diesel engine of the present invention, and FIG. 2 is a perspective view showing a means for connecting the control slider and valve body in the unit injector of FIG. 1. , FIG. 3 is an enlarged vertical cross-sectional view showing the connection between the feed hole of the control slider and the plunger lead in the unit injector shown in FIG. 1, and FIG. FIG. 6 is an enlarged longitudinal cross-sectional view showing the communication state between the feed hole of the control slider and the lead of the plunger that has been slid downward with movement. 10...Units used in diesel engines
Injector, 11... Valve body, 19... Needle spindle bore, 20... Valve seat,
21, 22...Nozzle port, 23...Fuel reservoir, 24...Nozzle needle, 31...Plunger bore, 32...
Slider bore, 33... Plunger, 34... Pump chamber, 35... Lead, 36... Communication path, 38... Control slider, 39... Feed hole,
40...fuel chamber, 41...hydraulic chamber, 42...slider
Return spring, 44...Fuel passage, 46...
Oil passage, 49...needle spring.

Claims (1)

[Scope of Claims] 1. A needle spindle bore having a valve seat and a nozzle, a plunger bore communicating with a fuel reservoir of the needle spindle bore, and a fuel reservoir in a predetermined portion of the plunger bore. A valve body with a slider bore communicating with the plunger bore to widen the plunger bore, and a needle spring to expand the valve body.
A nozzle needle is fitted into the needle spindle bore so as to be seated on the seat, and a nozzle needle is arranged to be reciprocally slidable in the plunger bore so as to form a pump chamber in the plunger bore. , and a plunger having a lead and a communication passage connecting the lead to the pump chamber; and a plunger fitted to the plunger so as to form a fuel chamber and a hydraulic pressure chamber in the slider bore; a control slider that is helically spline-coupled to the inner peripheral surface of the bore, is reciprocably disposed within the slider bore, and has a feed hole that connects the fuel chamber to the lead of the plunger; , a slider return spring disposed in at least one of the fuel chamber and the hydraulic chamber, a fuel passage formed in the valve body so as to connect the fuel chamber to the feed pump side, and the hydraulic chamber. A unit injector used in diesel engines that includes an oil passage formed in its valve body so that it can communicate with the control oil pump side.